1. Field of the Invention
The present invention relates to a transmission, and a method of shift control for transmission. In particular, it relates to a dual-clutch transmission comprising two clutches, and a method of shift control for such dual-clutch transmission.
2. Description of the Related Art
One of transmissions for automobile is a dual-clutch transmission that comprises two clutches, namely, which uses a so-called dual-clutch mechanism, (hereinafter abbreviated to as “DCT”). Upon switching change-speed stages, the DCT is characterized in that it can carry out shifting operations quickly without cutting off or interrupting torque transmissions.
As disclosed in Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2007-292,250, for instance, a DCT is controlled for changing speeds so that it can change speeds quickly in accordance with change-speed requests. That is, when a vehicle is traveling with a change-speed stage, which is set on an input shaft that corresponds to one of the clutches being connected, the DOT preliminarily selects (or pre-shifts to) another change-speed stage, which is set on another input shaft that corresponds to the other one of the clutches being disconnected. The DCT usually determines a change-speed stage, which it selects in advance, using a current vehicular condition, such as a vehicle speed and an accelerator opening magnitude, while consulting a shift map.
However, when a driver carries out change-speed operations by a conventional transmission that uses a shift map, he or she might feel slowness or retard to suffer from feelings of annoyance or unpleasantness because ordinary traveling conditions are simulated to prepare the shift map. That is, when a selected change-speed stage might not be appropriate upon restarting or accelerating a vehicle after rapid deceleration, the conventional transmission reselects another change-speed stage and shifts to it again. As a result, the driver might feel annoyance or unpleasantness because of the time that has elapsed since he or she has issued a change-speed request. Alternatively, he or she might feel annoyance or unpleasantness because the conventional transmission has shifted to an inappropriate change-speed stage. Moreover, even during deceleration, the conventional transmission might give the driver feelings of annoyance or unpleasantness because it might select the change-speed stage one after another accompanied by rapid changes in the vehicle speed to result in the occurrence of torque fluctuation.